Emerging Pollutant Emissions to Water

Environmental Quality Standards Directive compliant analytical techniques

by Dr Claire Stone

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It was in 2008 that the European Parliament and Council first published the Environmental Quality Standards Directive. This publication lays down environmental quality standards (EQS) for priority substances and certain other pollutants as provided for in Article 16 of the Water Framework Directive 2008/105/EC (WFD), with the aim of achieving good surface water chemical status and in accordance with the provisions and objectives detailed in the Directive.

As a European wide directive, each member state has a plan for assessing their water bodies and to achieve compliance with the concentrations (annual average and maximum) set out in the document. Annual average (AA) EQS and maximum allowable concentrations (MAC) EQS protect against long-term exposure and short-term peak concentrations, respectively, and are listed in Annex I to the Directive. For any given surface water body, applying the MACEQS means that the measured concentration at any representative monitoring point within the water body does not exceed the standard.

Originally the directive listed 36 priority substances and other pollutants (or groups of pollutants), however in 2013 the directive was revised again with further pollutants added to the list and changes made to the annual average and maximum pollutant concentrations.

“changes to the Environmental Quality Standards directive are causing considerable challenges to the environmental testing laboratory sector”

Revisions to the guidelines add pollutants to the lists of designated chemicals which are either not commonly tested for or where the concentration levels permitted (and thus to be measured) are considerably lower than most current standard laboratory detection levels. As a consequence, changes to the directive are causing considerable challenges to the environmental testing laboratory sector. Of note is that the revisions to the directive apply from 2015 through to 2021 and new pollutants apply from 2018, and in some cases these only apply if analytical techniques exist to support the EQS levels set out in the directive. Each member state is also required to instigate a “watch list” to monitor the occurrence of emerging pollutants, the aim being to report back to REACH and other source control regulators to ensure necessary additional measures are put in place to reduce pollutant release where possible, within the UK this is called the “Chemical Investigation Programme”.

A review of the watch list was carried out in 2018 and five substances were removed from the watch list; however further compounds were added: 17-Alpha-ethinylestradiol (EE2), 17-Beta-estradiol (E2), estrone (E1), Macrolide antibiotics (erythromycin, clarithromycin, azithromycin), Methiocarb, Neonicotinoids (imidacloprid, thiacloprid, thiamethoxam, clothianidin, acetamiprid), Metaflumizone, Amoxicillin and Ciprofloxacin.

Many of these compounds reach water bodies through the waste water treatment process; such as the antibiotics and estrone and estradiol compounds. Care therefore needs to be given to monitoring these processes for effectiveness and subsequent emissions of these compounds into surface waters.

Analytically, the compounds listed in Annex I to the Directive are generally most challenging to determine in complex matrices at low concentrations; in addition to those new compounds flagged on the 2018 watch list revision. For these we need to turn to chromatographic techniques for their analysis.

Monitoring Maximum Allowable Concentrations

Annex I to the 2008/105/EC Directive lists MAC (Maximum Allowable Concentrations) for approximately a third of the substances of interest. Considering compounds amenable to chromatographic analysis, the list reduces to the following compounds:

  • Alachlor
  • Anthracene
  • Atrazine
  • Benzene
  • C10-C13 Chloroalkanes
  • Chlorfenvinphos
  • Chlorpyrifos
  • Diuron
  • Endosulfan
  • Fluoranthene
  • Hexachlorobenzene
  • Hexachlorbutadiene
  • Hexachlorocyclohexane
  • Isoproturon
  • 4-Nonylphenol
  • Pentachlorophenol
  • Benzo(a)pyrene
  • Simazine
  • Tributytin compounds

Polyaromatic hydrocarbons

To highlight the differences and challenges in analysing compounds within this Directive, polyaromatic hydrocarbon (PAH) compounds can be easily compared and contrasted.

Anthracene (C14H10) is a PAH with a relatively low solubility in water of 44 µg/l. It is a component of coal tar and has been widely used as a wood preservative, in insecticides and as a coating material. It is not a known carcinogen. It has a relatively high EQS level of 0.1 µg/l compared with that of benzo(a)pyrene.

Benzo (a)pyrene is a group 1 carcinogen with mutagenic and highly carcinogenic metabolite. It is also found as a component of coal tar and is released into the environment typically through combustion. It is sparingly soluble in water with a solubility between 0.2 – 6.2 µg/l.

Both of these compounds are commonly tested for, with the most widely used technique being gas chromatography – mass spectroscopy (GC-MS). The compounds are extracted from the water by either liquid/liquid or solid phase extraction and the resulting solvent is injected into the GC-MS. Typical reporting limits are around 0.01 µg/l. For both compounds this is within the range of interest for the MAC and the EQS level for anthracene; however it’s clearly not suitable for the analysis of benzo(a)pyrene at the EQS level.

“the EQS level for benzo(a)pyrene is around 50 x lower than the standard reporting limit, and this calls for more advanced extraction and analysis techniques”

The EQS level for benzo(a)pyrene is around 50 x lower than the standard reporting limit, and this calls for more advanced extraction and analysis techniques. As these compounds lend themselves to liquid / liquid or solid phase extraction techniques, the sample can be “preconcentrated” by using a larger volume of sample, however this would typically require the handling of samples in excess of 25 litres in size which is not practical from either the sampling perspective or during preparation at the laboratory. The resulting solvent could then be concentrated to a smaller volume and analysed by a more sensitive technique such as GC-MS/MS. Much as this sounds relatively straightforward and a combination of the two renders this reporting limit feasible, consideration has to be given to sample concentration steps as by concentrating the analyte, the concentration of background and interference signals may also increase. Also, instrumental resolution and peak shift may be problematic, notwithstanding the challenge of finding environmental matrices with a sufficiently low pollutant level in order to validate the method and prove the detection and/or reporting limit.

Hexachlorocyclohexanes

Hexachlorocyclohexanes are all insecticides, the α- and β- forms being by-products from the formulation and production of Lindane. Lindane is a broad spectrum insecticide used to treat both soils and seeds. It bioconcentrates rapidly and is prone to long range transport. These compounds are particularly persistent in colder regions of the world; bioaccumulating and biomagnifiying in Arctic food webs. They are all classified as potential human carcinogens.

The MAC concentration is not analytically challenging and the EQS level is only 10 fold lower and as such we can turn to routine chromatographic methods for the detection of these isomers, however powerful modern deconvolution software aids detection when such chemically similar compounds are present in mixtures.

New watch list compounds

Compounds added to the watch list prove to be analytically challenging. These compounds make their way on to the watch list through being determined and quantified in a range of water bodies and/or at discharge points to water bodies (water treatment works); and as such methods do exist; however often a great deal of care needs to be taken in performing the analysis.

Steroids

Estrone (E1), 17β estradiol (E2), and 17α ethinylestradiol (EE2); also known as synthetic oestrogenics and make their way into water bodies as they may not be broken down in the body and as such may pass through the water treatment facilities unchanged.

For analysis the compounds need to be concentrated and derivatised to enable final analysis and detection by liquid chromatography with mass spectral detection. Due to the complex nature of the analysis it is necessary to use MS/MS technology to effectively eliminate interferences and generate a clear response. A key area to consider in this process is laboratory and personnel background – including those involved in the sampling process.

Antibiotics

Macrolide antibiotics (erythromycin, clarithromycin, azithromycin) appeared on the list of compounds of interest as they are used extensively and a significant portion of these may pass through the body without being metabolised.

“with the European Water Framework directive being revised every two years and each member state setting a programme of “chemical investigation” this legislation is constantly evolving”

The analysis of these compounds is complex, and their metabolites are often detected along with the compounds themselves. They are best analysed by LC-MS/MS; employing the MS/MS technology to effectively select the ions of interest for each chromatographic separation obtained by liquid chromatography. With this set up it is possible to achieve an analytical range of 10 – 1000 ng/L; which is in the range of expected concentrations given in the watch list review of 2018.

Analytical innovation?

The original EQS (2008) supporting documentation does give some guidance on standard analytical methods which may be employed for the analysis of pollutants however, even at this time it was acknowledged that standard methods may not meet the required levels and since 2013 most of the EQS levels have been revised to lower values. EQS levels are largely derived from ecological and human toxicology data and as such are not necessarily representative of what existing laboratory techniques are able to deliver, hence the setting of an EQS is a key driver in the innovation cycle for new and improved techniques.

Within the remit of the directive, often new pollutants are identified, and thus a new EQS set and the cycle continues. With the European Water Framework directive being revised every two years and each member state setting a programme of “chemical investigation” this legislation is constantly evolving and it can only be hoped that analytical techniques and capabilities are able to keep up with the rate of change. As these changes come through; more complex analytes are likely to have maximum allowable concentrations set and in turn ultra low environmental quality standards are likely to be set.

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